Many times while entering search phrases into Google, we find a lot of somewhat related websites, but hardly ever anything exact. So why bother on getting these supposedly un-searched terms? It’s very simple; because there is a general perception that having your website in the No. 1 spot in Google means that your website is an authority on that particular subject. Agreeably, any experienced user knows, this is most often not the case, but then again, perception is reality.
Granted, some of the search phrases that you can get ranked on may or may not be very popular, but you never know what a user is going to enter into the search box. Nor do we ever know what exact information they are actually searching for.
One of the most common traits of searching is that when a user first begins a search, they use a broad term, but as they go further along into their search, the phrases become more precise as the users themselves filter out the un-related websites.
This is the same concept on which a successful PPC campaign can be run. While it may indeed be great to get tons of traffic for the keyword "shoes", if a user is really looking for "Nike running shoes", the website has wasted money on that search.
Another curious statistic that web analytics reveal is that consumers who come to a website through a PPC are not “life-time” customers. They are usually interested in the quick fix, or easy solution. However users who arrives through organic search engine optimization, are more likely to be lifetime consumers since they tend to trust a company that has "earned" it's way to the top of the rankings.
By the time a user has a four to five keyword phrase entered in for their search query, there is a chance that they have already eliminated the "noise" and are focused on the "signal" i.e. the product or service that your website is offering.
One final item to remember is that if you have an exact phrase that is not common to a search engine query, once it gets indexed, it will most likely appear in the number one position since the search engines always try to find an exact match when other factors aren't available.